<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>盒子模型的层级</title>
    <style>
        *{
            margin:0;
            padding:0;
        }
        div{
            height:200px;
            width:800px;
            background: #6fa026;
            margin:0 auto;
            position:relative;
        }
        ul{
            list-style: none;
        }
        img{
            height:200px;
            width:800px;
            position:absolute;
        }
        .btn li{
            height:10px;
            width:10px;
            border:1px solid black;
            float:left;
            border-radius: 50%;
            margin-left:5px;
        }
    </style>
</head>
<body>
    <div>
        <!--<ul class="img">-->
            <!--<li><img style="z-index:1" src="https://res.shiguangkey.com//file/201806/19/20180619142252602590185.jpg" alt=""></li>-->
            <!--<li><img style="z-index:0" src="https://res.shiguangkey.com//file/201806/21/20180621150342030454625.jpg" alt=""></li>-->
        <!--</ul>-->
        <!--<ul class="but">-->
            <!--<li>&lt;</li>-->
            <!--<li>&gt;</li>-->
        <!--</ul>-->
        <ul class="btn">
            <li></li>
            <li></li>
            <li></li>
            <li></li>
        </ul>
    </div>
</body>
</html>